Holding hands as they walked through the school gates, some fighting back tears, 75 children who survived South Korea's worst maritime disaster in 20 years have returned to class vowing to remember their lost friends.

Wailing parents of the 250 children who did not survive, when a ferry taking them on a school trip capsized and sank, greeted the children outside the Danwon Highschool.

Some grieving parents held signs, one of which read: "We love you".

"Grownups are constantly telling us to forget and cheer up," an 18-year-old boy who spoke for the survivors said, fighting back tears. "But we will remember and recollect our friends. Because not forgetting them is what we can do at best. Just as we will remember them, please don't forget them."

Two months after the Sewol ferry sank and killed more than 300 passengers, the surviving children were brought to school in five buses under a police escort.

Many were wearing bracelets engraved with the message, "Remember 0416," and all were accompanied by their parents.

On April 16, the Sewol ferry sharply listed and capsized on a routine overnight journey from Incheon, the port city one hour drive from the children's hometown, to the vacation island of Jeju, overloaded with cargo and sailing too fast on a turn.

Most of the 325 students who listened to the order to stay in the cabins were trapped as the vessel sank and paid for their obedience with the lives.

"Our friends and teachers had to leave us because of irresponsible and selfish adults," said one of the students before going to class.

The 15 surviving crew members are on trial, with four including the captain charged with homicide, amid a national outcry of anger after video footage showed them fleeing the vessel as it began to list after telling passengers to stay put.

The government of President Park Geun-hye has also been bitterly criticised for the slow and ineffective handling of the disaster and the incompetence displayed in the rescue operation.

The prime minister has resigned and Park has announced the break-up of the Coast Guard citing incompetence.

A massive manhunt has failed to capture the man seen as the effective owner of the company that operated the ferry. Yoo Byung-un is wanted on charges of embezzlement stemming from his control over a web of business interests owned by his sons, including Chonghaejin Marine, the ferry operator.

For the survivors and their parents, the two months since the sinking has been a painful time of soul searching, debating whether to transfer to other schools.

But they ultimately decided to return to the familiar surrounds of Danwon Highschool and try and heal the emotional scars, receiving therapy at the school, said Park Suck-soon, the father of one of the survivors.

"The kids are coming back to school, carrying the terrible experience of having gone through the ship sinking and the evacuation and losing their friends and teachers," he said, adding "Don't forget April 16".